Authorities arrested and charged Friday a Virginia man allegedly on his way to the U.S. Capitol for what he thought would be a suicide attack on one of the nation’s most symbolic landmarks. The federal criminal complaint against the suspect identifies him as Amine El Khalifi, a 29-year-old Moroccan citizen who has been living in the United States illegally since 1999 after his visa expired.

He was nabbed following a lengthy investigation by the FBI, initiated after he allegedly expressed interest in conducting an attack. Court documents say he came onto the radar screen in early December after he told an undercover agent about an earlier plan to bomb a northern Virginia building.

The FBI said it conducted an undercover operation as part of a longstanding terrorism probe of the suspect, who was arrested blocks from the Capitol building as he allegedly hoped to detonate what he believed to be live explosives.

“Explosives the suspect allegedly sought to use in connection with the plot had been rendered inoperable by law enforcement and posed no threat to the public,” the Federal Bureau of Investigation said in a statement.